The general objectives of the proposed work are to define some of the interactions between biologically active peptides from blood and specific target cells in the lung. It is of interest and importance to relate these interactions to tissue injury and inflammation. There is particular emphasis upon the actions of peptides such as C3a anaphylatoxin and the kinin peptides on endothelial cells, and the mechanisms of inactivation of these mediators. We have established that cultured human endothelial cells metabolize and inactivate several vasoactive peptides. The studies are now extended to the actions of peptides on the endothelial cells. BIBLIOGRAPHIC REFERENCES: Johnson, A.R. and Erdos, E.G.: Metabolism of vasoactive peptides by human endothelial cells in culture: Angiotensin I converting enzyme (kininase II) and angiotensinase. J. Clin. Invest. in press, April, 1977. Johnson, A. R. and Erdos, E.G.: Inactivation of Substance P by human vascular endothelial cells (Abstract) Fed. Proc. 36: 1014, 1977.